National Guard troops stationed on the U.S. Mexico-border from Texas to California may leave their current positions next month unless Congress agrees to pay for a longer deployment, Homeland Security Secretary Janet Napolitano said Tuesday.

Napolitano said the troops, who are currently aiding local law enforcement efforts in the border region, are only funded through the the federal government’s current fiscal year, which ends on Sept. 30. It is up to Congress, she said, to decide “whether and how that mission should be continued.”

The Obama administration’s top border security official said the National Guard personnel have been “very helpful” to state and local officials and have been “a great add-on” to existing law enforcement efforts. Still, their mission could end unless Congress acts.

Thus far, she said, “Congress has declined to do that.”

Without congressional action, Napolitano said her department would see if Department of Defense money could be “reprogrammed” for the mission. It would be up to the Pentagon to decide “whether DOD has the resources” to continue the National Guard activities along the border.

Catherine Frazier, a spokeswoman for Texas Gov. Rick Perry, said the Obama administration had failed to secure the borders and blamed Napolitano for failing to persuade Congress to appropriate the needed funds.

“It’s her responsibility to be fighting for the resources,” Frazier said.